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Silkworm larvae as an animal model of bacterial infection pathogenic to humans
Chikara Kaito1, Nobuyoshi Akimitsu, Haruo Watanabe
1Graduate School of Pharmaceutical Sciences, The University of Tokyo, 3-1, 7-Chome, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Abstract:
Silkworm larvae, Bombyx mori, were examined as an animal model of human infection with pathogenic bacteria. When 3 x 10(7) cells of Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa, or Vibrio cholerae were injected into the blood of fifth instar silkworm larvae, over 90% of the larvae died within 2 days, whereas over 90% survived for 5 days after injection of the same amount of Escherichia coli. Growth of S. aureus was observed in larvae blood and tissues. Immunostaining analysis revealed that S. aureus proliferated at the surface of the midgut. Infection of silkworm larvae by methicillin-sensitive S. aureus was cured by ampicillin, oxacillin, and vancomycin, whereas infection by methicillin-resistant S. aureus was not cured by ampicillin or oxacillin, although vancomycin was effective. Disinfectants were not effective because of toxicity against the larvae. Thus, silkworm larvae are useful for evaluating antibiotics for pathogenic bacterial infection in humans.
Insights
Silkworm larvae serve as a valuable animal model for studying bacterial infections. They effectively model human infections and help evaluate antibiotic efficacy against pathogens like Staphylococcus aureus.
Area of Science:
- Microbiology
- Infectious Diseases
- Animal Models
Background:
- Pathogenic bacteria pose a significant threat to human health.
- Developing effective treatments requires reliable animal models for infection studies.
Purpose of the Study:
- To evaluate silkworm larvae (Bombyx mori) as an animal model for human bacterial infections.
- To assess the efficacy of various antibiotics against specific bacterial pathogens in this model.
Main Methods:
- Injection of pathogenic bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, Vibrio cholerae, Escherichia coli) into silkworm larvae.
- Observation of larval survival rates and bacterial growth within larvae.
- Immunostaining to visualize bacterial proliferation.
- Testing antibiotic and disinfectant efficacy against infections.
Main Results:
- High mortality rates observed in larvae infected with S. aureus, P. aeruginosa, and V. cholerae within 2 days.
- E. coli infection showed higher survival rates.
- S. aureus proliferation was confirmed in larval tissues, particularly the midgut.
- Vancomycin effectively treated methicillin-resistant S. aureus infections, while ampicillin and oxacillin were ineffective.
Conclusions:
- Silkworm larvae are a suitable and cost-effective animal model for studying pathogenic bacterial infections.
- This model can be used to evaluate the effectiveness of antibiotics, including against antibiotic-resistant strains.
- Disinfectants showed toxicity, limiting their use in this model.